The invention relates to magnetic heads, head assemblies or transducers and more particularly to such heads which provide a tunnel erasing action by means of erasing core portions having gaps therebetween on an active face of the head on opposite sides of a central read/write core having a read/write gap in said active face.
Magnetic heads of this general description have previously been suggested, such as in Castrodale et al U.S. Pat. No. 4,110,804. The magnetic head assembly disclosed in this patent includes a central read/write core having a read/write winding on one of the legs of the core and a pair of erase cores on the two sides of the read/write core. Erase gaps are provided in the two erase cores and are positioned quite close to a read/write gap in the read/write core longitudinally of the active face of the transducer on which the magnetic medium used in connection with the transducer travels so that the erase cores and the read/write core overlap to some extent. A single erase winding is disposed about the two erase cores and magnetically links the erase cores. Such a magnetic head functions very well under most circumstances; however, since portions of the erase cores and erase magnetic circuits overlap and run parallel to a portion of the read/write core and the read/write magnetic circuit, the DC induced flux in the erase cores causes a bias on the read/write magnetic circuit.
Such bias would be minimized by using a single erase core with two erase gaps in series therein and having a single energizing winding thereon, with the flux flowing in a single path through the two erase gaps and cross ways through a portion of the associated write core from one erase gap to the other. Such a construction is shown in Bos et al, U.S. Pat. No. 3,485,958 in which the erase core constitutes a U-shaped piece having a winding on its central leg, with the ends of the U-shaped piece forming the erase gaps in conjunction with a part of the read/write core on the active face of the transducer. The lengths of the erase gaps and the flux flowing through these gaps are transverse of the active transducer face and the direction of movement of the magnetic medium across the active face, and the erase gap lengths are thus of the same dimension as the widths of the edge magnetic track portions to be erased on the magnetic medium. Therefore, if the portions of a magnetic track to be erased have substantial width, the lengths of the erase gaps have this same substantial dimension; and very considerable power is needed in order to provide an effective erase flux in these erase gaps.